Chapter 2, Modeling with UML, Part 2

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1 Object-Oriented Software Engineering Using UML, Patterns, and Java Chapter 2, Modeling with UML, Part 2 Outline of this Lecture Use case diagrams Describe the functional behavior of the system as seen by the user. Class diagrams Describe the static structure of the system: Objects, attributes, associations. Sequence diagrams Describe the dynamic behavior between objects of the system. Statechart diagrams Describe the dynamic behavior of an individual object. Activity diagrams Describe the dynamic behavior of a system, in particular the workflow. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 2 What is UML? Unified Modeling Language Convergence of different notations used in objectoriented methods, mainly OMT (James Rumbaugh and collegues), OOSE (Ivar Jacobson), Booch (Grady Booch) They also developed the Rational Unified Process, which became the Unified Process in year at GE Research, where he developed OMT, joined (IBM) Rational in 1994, CASE tool OMTool At Ericsson until 1994, developed use cases and the CASE tool Objectory, at IBM Rational since 1995, Developed the Booch method ( clouds ), ACM Fellow 1995, and IBM Fellow com/ UML Nonproprietary standard for modeling systems Current Version: UML 2.2 Information at the OMG portal Commercial tools: Rational (IBM),Together (Borland), Visual Architect (Visual Paradigm), Enterprise Architect (Sparx Systems) Open Source tools ArgoUML, StarUML, Umbrello (for KDE), PoseidonUML Example of research tools: Unicase, Sysiphus Based on a unified project model for modeling, collaboration and project organization Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 4 UML: First Pass You can solve 80% of the modeling problems by using 20 % UML We teach you those 20% rule: Pareto principle Vilfredo Pareto, Introduced the concept of Pareto Efficiency, Founder of the field of microeconomics. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 5 UML First Pass (covered in Last Lecture) Use case diagrams Describe the functional behavior of the system as seen by the user Class diagrams Describe the static structure of the system: Objects, attributes, associations Sequence diagrams Describe the dynamic behavior between objects of the system Statechart diagrams Describe the dynamic behavior of an individual object Activity diagrams Describe the dynamic behavior of a system, in particular the workflow. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 6

2 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 7 UML Basic Notation: First Summary UML provides a wide variety of notations for modeling many aspects of software systems In the first lecture we concentrated on: Functional model: Use case diagram Object model: Class diagram Dynamic model: Sequence diagrams, statechart Now we go into a little bit more detail UML Use Case Diagrams PurchaseTicket Used during requirements elicitation and analysis to represent external behavior ( visible from the outside of the system ) An Actor represents a role, that is, a type of user of the system A use case represents a class of functionality provided by the system Use case model: The set of all use cases that completely describe the functionality of the system. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 8 Actors An actor is a model for an external entity which interacts (communicates) with the system: User External system (Another system) Physical environment (e.g. Weather) An actor has a unique name and an optional description Optional Description Examples: : A person in the train GPS satellite: An external system that provides the system with GPS coordinates. Use Case PurchaseTicket A use case represents a class of functionality provided by the system Use cases can be described textually, with a focus on the event flow between actor and system The textual use case description consists of 6 parts: 1. Unique name 2. Participating actors 3. Entry conditions 4. Exit conditions 5. Flow of events 6. Special requirements. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 9 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 10 Textual Use Case Description Example 1. : Purchase ticket 2. Participating actor: 3. Entry condition: stands in front of ticket distributor has sufficient money to purchase ticket 4. Exit condition: has ticket PurchaseTicket 5. Flow of events: 1. selects the number of zones to be traveled 2. Ticket Distributor displays the amount due 3. inserts money, at least the amount due 4. Ticket Distributor returns change 5. Ticket Distributor issues ticket 6. Special requirements: None. Uses Cases can be related Extends Relationship To represent seldom invoked use cases or exceptional functionality Includes Relationship To represent functional behavior common to more than one use case. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 11 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 12

3 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 13 The Relationship relationships model exceptional or seldom invoked cases OutOfOrder PurchaseTicket Cancel The exceptional event flows are factored out of the main event flow for clarity The direction of an relationship is to the extended use case Use cases representing exceptional flows can extend more than one use case. NoChange TimeOut The <<includes>> Relationship <<includes>> relationship represents common functionality needed in more than one use case <<includes>> behavior is factored out for reuse, not PurchaseMultiCard because it is an exception The direction of a PurchaseSingleTicket <<includes>> relationship is <<includes>> to the using use case (unlike <<includes>> the direction of the relationship). NoChange CollectMoney Cancel Cancel Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 14 Class Diagrams Classes Type Class diagrams represent the structure of the system Used during requirements analysis to model application domain concepts during system design to model subsystems during object design to specify the detailed behavior and attributes of classes. zone2price getzones() getprice() Attributes Operations Table zone2price Enumeration getzones() Price getprice(zone) Signature Table zone2price Enumeration getzones() Price getprice(zone) Trip zone:zone Price: Price A class represents a concept A class encapsulates state (attributes) and behavior (operations) Each attribute has a type Each operation has a signature Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 15 The class name is the only mandatory information Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 16 Instances Actor vs Class vs Object tarif2006: zone2price = { { 1, 0.20}, { 2, 0.40}, { 3, 0.60}} : zone2price = { { 1, 0.20}, { 2, 0.40}, { 3, 0.60}} An instance represents a phenomenon The attributes are represented with their values The name of an instance is underlined The name can contain only the class name of the instance (anonymous instance) Actor An entity outside the system to be modeled, interacting with the system ( ) Class An abstraction modeling an entity in the application or solution domain The class is part of the system model ( User, Ticket distributor, Server ) Object A specific instance of a class ( Joe, the passenger who is purchasing a ticket from the ticket distributor ). Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 17 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 18

4 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 19 Associations 1-to-1 and 1-to-many Associations Country 1 1 City Enumeration getzones() Price getprice(zone) TripLeg Price Zone name:string 1-to-1 association name:string Associations denote relationships between classes The multiplicity of an association end denotes how many objects the instance of a class can legitimately reference. Polygon draw() Point x: Integer y: Integer 1-to-many association Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 20 Many-to-Many Associations From Problem Statement To Object Model Problem Statement: A stock exchange lists many companies. Each company is uniquely identified by a ticker symbol Class Diagram: Lists Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 21 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 22 From Problem Statement to Code Problem Statement : A stock exchange lists many companies. Each company is identified by a ticker symbol Class Diagram: Lists Java Code public class { private Vector m_ = new Vector(); }; public class { public int m_; private Vector m_ = new Vector(); }; Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 23 Associations are mapped to Attributes! Aggregation An aggregation is a special case of association denoting a consists-of hierarchy Exhaust system The aggregate is the parent class, the components are the children classes Muffler diameter Tailpipe diameter A solid diamond denotes composition: A strong form of aggregation where the life time of the component instances is controlled by the aggregate. That is, the parts don t exist on their own ( the whole controls/destroys the parts ) TicketMachine ZoneButton Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 24 3

5 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 25 Qualifiers Qualification: Another Example Without qualification Directory 1 With qualification File filename Lists Directory filename File Qualifiers can be used to reduce the multiplicity of an association Lists 1 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 26 Inheritance Button Packages Packages help you to organize UML models to increase their readability We can use the UML package mechanism to organize classes into subsystems CancelButton ZoneButton Inheritance is another special case of an association denoting a kind-of hierarchy Inheritance simplifies the analysis model by introducing a taxonomy The children classes inherit the attributes and operations of the parent class. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 27 Any complex system can be decomposed into subsystems, where each subsystem is modeled as a package. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 28 Object Modeling in Practice Object Modeling in Practice: Brainstorming Foo Dada Foo Class Identification: of Class, Attributes and Methods Is Foo the right name? Is Foo the right name? Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 29 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 30

6 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 31 Object Modeling in Practice: More classes Object Modeling in Practice: Associations Id?? Id I d has? 1) Find New Classes 2) Review s, Attributes and Methods 1) Find New Classes 2) Review s, Attributes and Methods 3) Find Associations between Classes 4) Label the generic associations 5) Determine the multiplicity of the associations 6) Review associations Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 32 Practice Object Modeling: Find Taxonomies Id I d Has () Practice Object Modeling: Simplify, Organize Id I d Show Taxonomies separately Savings Checking Mortgage Savings Checking Mortgage Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 33 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 34 Practice Object Modeling: Simplify, Organize Id I d Use the 7+-2 heuristics or better 5+-2! Has () Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 35 Sequence Diagrams Focus on Controlflow selectzone() TicketMachine Used during analysis To refine use case descriptions to find additional objects ( participating objects ) Used during system design TicketMachine to refine subsystem interfaces insertcoins() zone2price Instances are represented Messages -> by selectzone() rectangles. ActorsOperations by sticky on insertcoins() figures participating Object pickupchange() pickupchange() pickupticket() Lifelines are represented by dashed lines Messages are represented by arrows pickupticket() Activations are represented by narrow rectangles. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 36

7 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 37 Sequence Diagrams can also model the Flow of Data selectzone() Dataflow ZoneButton Display lookupprice(selection) price displayprice(price) continued on next slide... The source of an arrow indicates the activation which sent the message Horizontal dashed arrows indicate data flow, for example return results from a message Sequence Diagrams: Iteration & Condition insertchange(coin) Iteration Condition ChangeProcessor continued from previous slide... lookupcoin(coin) price CoinIdentifier Display CoinDrop displayprice(oweda mount) [oweda mount<0] returnchange(-oweda mount) continued on next slide... Iteration is denoted by a preceding the message name Condition is denoted by boolean expression in [ ] before the message name Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 38 Creation and destruction Sequence Diagram Properties continued from previous slide... ChangeProcessor createticket(selection) Ticket print() free() Creation of Ticket Destruction of Ticket UML sequence diagram represent behavior in terms of interactions Useful to identify or find missing objects Time consuming to build, but worth the investment Complement the class diagrams (which represent structure). Creation is denoted by a message arrow pointing to the object Destruction is denoted by an X mark at the end of the destruction activation In garbage collection environments, destruction can be used to denote the end of the useful life of an object. Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 39 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 40 Outline of this Class A more detailed view on Use case diagrams Class diagrams Sequence diagrams Activity diagrams Activity Diagrams An activity diagram is a special case of a state chart diagram The states are activities ( functions ) An activity diagram is useful to depict the workflow in a system Handle Document Archive Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 41 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 42

8 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 43 Activity Diagrams allow to model Decisions Open Decision [lowpriority] Allocate Activity Diagrams can model Concurrency Synchronization of multiple activities Splitting the flow of control into multiple threads [fire & highpriority] [not fire & highpriority] Notify Fire Chief Splitting Allocate Synchronization Notify Police Chief Open Coordinate Archive Document Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 44 Activity Diagrams: Grouping of Activities Activities may be grouped into swimlanes to denote the object or subsystem that implements the activities. Activity Diagram vs. Statechart Diagram Statechart Diagram for Focus on the set of attributes of a single abstraction (object, system) Event causes state transition Allocate Dispatcher Active Inactive Closed Archived - Handled - Docu mented - Archived Open Coordinate Archive Activity Diagram for (Focus on dataflow in a system) Docu ment FieldOfficer Handle Completion of activity causes state transition Document Triggerless transition Archive Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 45 Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 46 UML Summary UML provides a wide variety of notations for representing many aspects of software development Powerful, but complex UML is a programming language Can be misused to generate unreadable models Can be misunderstood when using too many exotic features We concentrated on a few notations: Functional model: Use case diagram Object model: class diagram Dynamic model: sequence diagrams, statechart and activity diagrams Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 47